Accuracy and reliability of cone-beam computed tomography for measuring alveolar bone height and detecting bony dehiscences and fenestrations

S109

Original article

accuracy and reliability of cone-beam computed tomography for measuring alveolar bone height and detecting bony dehiscences and fenestrations Cynthia C. Leung,a Leena Palomo,b Richard Griffith,c and Mark G. Hansd

Cleveland, Ohio

Introduction: The purpose of this study was to evaluate the accuracy and reliability of cone-beam computed tomography (CBCT) in the diagnosis of naturally occurring fenestrations and bony dehiscences. In addition, we evaluated the accuracy and reliability of CBCT for measuring alveolar bone margins. Methods: Thirteen dry human skulls with 334 teeth were scanned with CBCT technology. Measurements were made on each tooth in the volume-rendering mode from the cusp or incisal tip to the cementoenamel junction and from the cusp or incisal tip to the bone margin along the long axis of the tooth. The accuracy of the CBCT measure-ments was determined by comparing the means, mean differences, absolute mean differences, and Pearson correlation coefficients with those of direct measurements. Accuracy for detection of defects was determined by using sensitivity and specificity. Positive and negative predictive values were also calculated. Results: The CBCT measurements showed mean deviations of 0.1 ± 0.5 mm for measurements to the cementoenamel junction and 0.2 ± 1.0 mm to the bone margin. The absolute values of the mean differences were 0.4 ± 0.3 mm for the cementoenamel junction and 0.6 ± 0.8 mm for the bone margin. The sensitivity and specificity of CBCT for fenestrations were both about 0.80, whereas the specificity for dehiscences was higher (0.95) and the sensitivity lower (0.40). The negative predictive values were high (≥0.95), and the positive predictive values were low (dehiscence, 0.50; fenestration, 0.25). The reliability of all measurements was high (r ≥0.94). Conclusions: By using a voxel size of 0.38 mm at 2 mA, CBCT alveolar bone height can be measured to an accuracy of about 0.6 mm, and root fenestrations can be identified with greater accuracy than dehiscences. (Am J Orthod Dentofacial Orthop 2010;137:S109-19)

Despite many reports in the literature on the various uses of cone-beam computed tomog-raphy (cBct), studies on its accuracy and

image quality for assessing bone morphology have been limited. also, no studies have assessed the use of cBct to study alveolar bone morphology in vivo. in-stead, most studies used radiographic phantoms, which do not accurately represent some anatomic structures such as tooth sockets and alveolar bone margins.1,2

Other studies have used human skulls, but the defects measured were created by the operator.3-6 Still other studies compared cBct to multi-slice spiral comput-ed tomography, multidetector-row helical computed tomography, or spiral computed tomography as gold standards.1,7 the problem with comparing cBct to other computed tomography (ct) machines is that all have some measurement errors.8-10 in addition, multi-slice spiral ct, multidetector-row helical ct, and spiral ct use more radiation and have higher costs, limiting their use for routine dental radiography.11-13

the first model of cBct that used a cone-beam x-ray instead of the traditional fan beam was the dy-namic spatial reconstructor introduced by Hoffman et al14 and ritman et al15 in 1980. this was developed to image a volume instead of a slice as in conventional ct with “stop-action” pulsed radiation to minimize blurring effects from motion and high-temporal reso-lution that were especially important for imaging the heart, lungs, and circulation. although the high tem-poral resolution of the dynamic spatial reconstruc-tor was useful in angiographic imaging with contrast

From the School of Dental Medicine, case Western reserve University, cleve-land, Ohio.aFormer resident, Department of Orthodontics; currently private practice, Brooklyn, nY. bassistant professor, Department of Periodontics.cassistant professor, Department of Orthodontics.dProfessor and chairman, Department of Orthodontics.the authors report no commercial, proprietary, or financial interest in the prod-ucts or companies described in this article.reprint requests to: Mark g. Hans, case Western reserve University, School of Dental Medicine, Department of Orthodontics, 10900 euclid ave, cleveland, OH 44106; e-mail, [email protected], September 2008; revised and accepted, July 2009.0889-5406/$36.00copyright © 2010 by the american association of Orthodontists.doi:10.1016/j.ajodo.2009.07.013

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S110 Leung et al American Journal of Orthodontics and Dentofacial OrthopedicsApril 2010

measurements. the second hypothesis was that there is no difference in the detection of dehiscences and fenestrations with a cBct imaging system compared with direct assessments on dry human skulls.

MateRIaL and MetHodS

Dry human skulls were selected from the Ha-mann-todd skull collection at the Bolton-Brush growth Study and the Museum of natural History in cleveland, Ohio. a preliminary screening of 39 skulls including 1040 teeth showed that the prevalences of dehiscences and fenestrations were approximately 11% and 8% of these teeth, respectively. these per-centages were equivalent to the average of the rates reported in the literature.38-43 a sample size estimate for a descriptive study by using proportions was de-termined to be 240 at confidence intervals of 99% and 1%.44 in addition, the sample size calculation for comparison of 2 groups by using a standardized ef-fective size of 0.25 mm based on previous studies at a 5% level of significance and an 80% power was found to be a minimum of 240. a sample of 13 skulls with 334 teeth was selected with these inclusion criteria: (1) adult skulls based on dentition, (2) intact skulls with both the maxilla and the mandible, (3) mini-mum of 10 teeth per jaw, (4) no obvious pathology (cyst or tumor in the alveolar process), and (5) no mechanical damage (chips, cracks, or breaks in the alveolar process).

the skulls were scanned by using a commercial-ly available cBct scanner (cB Mercuray, Hitachi Medical Systems american, twinsburg, Ohio). after ensuring that the machine’s calibration was correct, the skulls were positioned in the center of the scan-ning table in the same orientation as a live patient by using vertical and horizontal light guides (Fig 1). to allow visualization of both maxillary and mandibular cusps, the maxillary and mandibular dentitions were discluded with a cotton roll at the anterior region. the scanning parameters for imaging were 110 kVp, 2 ma, 9.6 seconds per revolution, and a 12-in field of view (FOV) (F mode). these settings produced a voxel size of 0.38 mm.45 the settings were the same as those used for orthodontic diagnosis and treatment planning in the graduate orthodontic clinic at case Western reserve University.

raw data were collected and reconstructed into 3-dimensional (3D) volumes by using the software from the manufacturer. the reconstructed data were export-ed and saved as digital imaging and communications in medicine (DicOM) files. the 512 two-dimensional slices were imported into a commercially available

agents, the volumetric anatomic structures generated were indistinct.16 additionally, the unit was not read-ily accessible, since it was expensive and weighed 13 tons.2 Over the past few decades, the dynamic spatial reconstructor evolved into the current cBct that uses less expensive x-ray tubes, along with more powerful personal computers and higher-quality de-tectors, allowing for relatively low radiation doses and smaller size requirements for operation, making cBct more affordable and feasible in smaller clinical office settings.17

according to the definition of carranza et al,18 fenestrations are isolated areas in which the root is denuded of bone, and the root surface is covered only by periosteum and overlying gingiva. Dehiscences are bony defects in which the denuded areas involve the alveolar bone margin. the presence of these buccal alveolar bone defects decreases the bony support for the teeth. it is well documented that, under certain conditions (eg, plaque-induced inflammation), a lack of bony support during orthodontic movement can be detrimental to the health of the teeth and the periodon-tium.19-21 in addition, orthodontic tooth movement can create alveolar bone defects.22-28 Until recently, bony dehiscences and fenestrations could not be visualized by traditional 2-dimensional radiography because of the superimposition of contralateral cortical bony or dental structures.29,30 the development of ct and es-pecially cBct has provided the means to visualize these defects 3 dimensionally.3,31 the literature has reported the accuracy of ct and cBct for measur-ing and identifying artificially created alveolar bone defects.3,4,6 However, no studies have evaluated the use of cBct to diagnose naturally occurring bony dehiscences and fenestrations in human skulls. also, no studies have determined the positive and negative predictive values when cBct is used to diagnose al-veolar bone defects. the purpose of this study was to evaluate the accuracy and reliability of cBct in the diagnosis of naturally occurring fenestrations and bony dehiscences.

in addition, we evaluated the accuracy and reli-ability of cBct to measure the alveolar bone mar-gins on dentate skulls. this is important because the identification of these alveolar bone defects before orthodontic treatment is helpful for the clinician when planning treatment. an undiagnosed buccal alveolar bone defect could occur in a few patients and cause greater potential for treatment relapse32,33 or gingival recession resulting in an unesthetic finish of orth-odontic treatment.34-37 the first hypothesis was that there is no difference in the measurement of alveo-lar bone height with cBct compared with physical

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American Journal of Orthodontics and Dentofacial Orthopedics Leung et al S111Volume 137, Number 4, Supplement 1

to display the cBct images for evaluation and analy-sis. the radiodensity in Hounsfield units (HU) was ad-justed by the operator to the threshold deemed optimal for visualization of the buccal alveolar bone (Fig 2).

software program (accurex, version 1.1, cybermed, Seoul, Korea) on a networked computer workstation (Windows nt, Dell, round rock, tex) for 3D volume rendering. the 3D volume-rendering mode was used

Fig 1. Positioning of skull for CBCT imaging: a, overview of skull position with the scanner; B, lateral view of skull and detector placement; C, frontal view of skull and detector placement; d, lateral view of skull with lateral light positioning guides; e, oblique view of skull with frontal light positioning guides.

Fig 2. Illustration of 3D volume rendering and optimization: a, 3D volume rendering with the manu-facturer’s default density threshold set at 410 HU at the upper limit and 20 HU at the lower limit; B, 3D volume rendering with density threshold optimized by the operator at –280 HU at the upper and –510 HU at the lower limit.

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(t-Fen2). Since each molar has at least 2 buccal cusps, the mesiobuccal and the distobuccal cusps were mea-sured individually. table i describes the variables used. Previous studies used varying criteria for the identifica-tion of dehiscences, ranging from any defect greater than 1 mm near the ceJ,41 to 4 mm apical to the interproximal bone crest,39,40,43 to exposure of half of the root.38,42 in this study, to distinguish a dehiscence from horizontal bone loss caused by periodontal disease, a dehiscence was de-fined as a V-shaped defect along the BM, with the dis-tance between the ceJ and the alveolar bone height 3 mm or greater. if a fenestration or dehiscence was found on the 3D volumetric view, it was further analyzed by us-ing the 2-dimensional slice data to verify the presence or absence of bone covering the root surface. Defects were recorded if no bone could be seen covering the root sur-face when examining the axial and coronal slices at the

Based on a preliminary skull study, the threshold win-dow was fixed for all skulls at –280 and –510 HU at the upper and lower limits, respectively.

Figure 3 illustrates the measuring technique for the cBct images. all measurements were made by the same operator (c.c.l.). Because of the tendency for fenestra-tions and dehiscences to occur on the labial and buccal surfaces, all measurements on the cBct images were made on the buccal surface parallel to the long axis of the tooth.42,46 the first reference point was the cusp tip (t) for the posterior dentition and the midincisal tip (t) for the anterior dentition. the second reference point was the cementoenamel junction (ceJ) for the first mea-surement, the alveolar bone margin (BM) for the second measurement, and, if there was a fenestration, the coronal border of the fenestration for the third measurement (t-Fen1) and the apical border for the fourth measurement

Fig 3. Illustration of measuring technique on CBCT: a, tooth of interest with the buccal surface ori-ented squarely on screen; B, tape line drawn parallel to the long axis of the tooth; C, measurement of T-CEJ from cusp tip to the most apical point on the CEJ along the long axis of the tooth; d, mea-surement of T-BM from cusp tip to the most apical point on the BM along the long axis of the tooth; e, measurement of T-Fen1 from cusp tip the most coronal border of a fenestration; F, measurement of T-Fen2 from cusp tip to the most apical border of a fenestration.

table I. Description of variables

Variable Description

Dehiscence Buccal or facial alveolar bone defect involving an alveolar margin 3 mm or greater and concurrent with a V-shaped BM. Periodontal recessions involving the interproximal bone were excluded.

Fenestration (Fen) a circumscribed defect on the buccal or facial alveolar bone exposing the root.t-ceJ the distance from the cusp tip to the ceJ parallel to the long axis of the tooth. Buccal cusps were used for posterior teeth

and midincisal tips were used for anterior teeth.t-BM the distance from the cusp tip to the most coronal bone margin measured along a line parallel to the long axis of

the tooth.t-Fen1 the distance from the cusp tip to the most coronal border of a fenestration along a line parallel to the long axis

of the tooth.t-Fen2 the distance from the cusp tip to the most apical border of a fenestration along a line parallel to the long axis of the tooth.Bone height the distance obtained from taking the difference between the measurements t-ceJ and t-BM. the reference points were

the same for a dehiscence.Dehiscence height the distance obtained from taking the difference between the measurements t-BM and t-ceJ.Fenestration height the distance obtained from taking the difference between the measurements t-Fen1 and t-Fen2.

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and Pearson correlation coefficients were used to esti-mate the relationship between the direct (digital cali-per) and indirect (cBct) methods. a P value of ≤0.05 was used to assign statistical significance. categorical data (presence or absence of fenestrations and dehis-cences) were analyzed by using 2 × 2 tables, and the sensitivity, specificity, and positive and negative pre-dictive values were calculated for both direct and indi-rect (cBct) methods. the direct method was used as the gold standard for comparison.

to determine the reliability of the methods, 65 ran-domly selected teeth (91 sites) were reexamined and re-measured with both methods at least 2 weeks after the initial measurements. the intraoperator reliability was as-sessed by calculating the intraclass correlation coefficient (icc) between measurements collected at both times.

ReSuLtS

the linear measurement accuracy of cBct was demonstrated by the means, mean differences, and ab-solute mean differences between each pair of direct and cBct measurements. Pearson correlation coefficients were also calculated for each pair of direct and indirect measurements. table iii shows these descriptive statis-tics for measurements of t to ceJ and t to BM for all sites examined. the means for both cBct and direct t-ceJ measurements were approximately equal (8.3 ± 1.4 vs 8.3 ± 1.5 mm), and the mean differences between the 2 methods showed that the cBct measurements

heights indicated by t-BM for dehiscences, and between t-Fen1 and t-Fen2 for fenestrations.

the same measurements were made directly on the skulls with a digital caliper calibrated to the near-est 0.01 mm (code no. 500-171-20, model no. cD-6-in cX Digimatic caliper, Mitutoyo american, Plymouth, Mich). to limit experimental bias, all measurements on the skulls were done at least 2 weeks after the cBct measurements. table ii shows the distribution of the teeth examined by tooth type. One hundred sixty-seven teeth were examined in both the maxillae and mandibles for a total of 334 teeth. a total of 446 measurements were made, since 2 reference points (mesial and distal cusps) were measured on the molars.

Statistical analysis

all statistical analyses were performed with the Statistical Package for Social Sciences (version 16.0, SPSS, chicago, ill). all linear measurements were adjusted for a known systematic software measure-ment error that underestimated the distance between 2 points by half of a voxel at each endpoint. therefore, 0.38 mm was added to each measurement to correct for this software error. For a complete discussion of this systematic error, see the study of Baumgaertel et al.47 Measurement accuracy was evaluated by comparing the means, mean differences, and absolute mean dif-ferences for linear measurements. two-tailed paired t tests were used to examine differences between means,

table II. Distribution of teeth examined by tooth type

Tooth type Maxilla Mandible Total

third molar 17 7 24Second molar 23 23 46First molar 23 22 45Second premolar 25 23 48First premolar 22 25 47canine 21 21 42lateral incisor 22 23 45central incisor 14 23 37total 167 167 334

table III. Measurement accuracy of t-ceJ and t-BM by means, mean difference (Mean Diff), absolute value of the mean difference (Mean abs), standard deviations, and correlations (n = 446)

Direct CBCTDifference

(direct-CBCT)Difference

(direct-CBCT)

Variable Mean ± SD (mm) Mean ± SD (mm) Mean Diff ± SD* Mean Abs ± SD† Correlation Significance

t-ceJ 8.3 ± 1.5 8.3 ± 1.4 –0.1 ± 0.5 0.4 ± 0.3 0.941‡ 0.002§t-BM 10.3 ± 2.1 10.6 ± 1.9 –0.2 ± 1.0 0.6 ± 0.8 0.871‡ 0.000§

*Mean difference between each direct and cBct measurement.†Mean of the absolute difference between each direct and cBct measurement.‡Pearson correlation coefficient is significant at the 0.01 level.§Paired 2-tailed t test is significant (P <0.01).

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at 0.81 (table Vi). For dehiscences, the specificity of cBct was 0.95, and the sensitivity was 0.42. the nega-tive predictive value for fenestrations, the probability that a negative test result (absence of fenestration) was truly negative, was 0.98, whereas the positive predictive value, the probability that a positive test result (presence

were essentially equal to the direct measurements (–0.1 ± 0.5 mm). the absolute mean differences showed a dif-ference of 0.4 ± 0.3 mm between the cBct and direct measurements; this was about the size of a voxel. the linear measurement, t-BM, was 0.2 ± 1.0 mm smaller on average for cBct, and the absolute mean difference was 0.6 ± 0.8 mm. Paired t tests showed a significant difference between cBct and direct measurements to both ceJ and BM (P ≤0.01). the correlation between cBct and direct methods for t-ceJ measurements was high (r = 0.94) as was the correlation for t-BM at 0.87.

the number of fenestrations detected by cBct was more than 3 times higher than for direct examination (104 fenestrations by cBct vs 32 by direct measure-ment; table iV). the number of dehiscences was less for cBct than for direct (43 dehiscences vs 52). Fenes-trations were detected more often in the maxilla than in the mandible for both cBct and direct measurements, whereas dehiscences were detected more often in the mandible than in the maxilla.

the cBct and direct results were analyzed by us-ing 2 × 2 contingency tables (table V). For fenestra-tions, the sensitivity and specificity of cBct were both

table IV. Summary of direct and cBct results for dehiscences and fenestrations by tooth type

Direct CBCT

Tooth type Sites (n) Fenestrations Dehiscences Fenestrations Dehiscences

Maxilla 230 24 22 81 16 third molar 34 2 1 3 1 Second molar 46 0 0 3 0 First molar 46 12 6 32 5 Second premolar 25 0 3 10 1 First premolar 22 2 4 13 4 canine 21 4 7 5 4 lateral incisor 22 3 0 9 1 central incisor 14 1 1 6 0Mandible 216 8 30 23 27 third molar 13 0 0 0 0 Second molar 44 0 1 0 2 First molar 44 0 2 1 3 Second premolar 23 1 1 4 2 First premolar 25 2 7 2 7 canine 21 1 5 7 5 lateral incisor 23 2 8 5 6 central incisor 23 2 6 4 2total 446 32 52 104 43

table VI. Sensitivity and specificity of cBct for de-tection of fenestrations and dehiscences

CBCT Fenestration Dehiscence

Sensitivitya 0.81 0.42Specificityb 0.81 0.95Positive predictive valuec 0.25 0.51negative predictive valued 0.98 0.93

aSensitivity is the probability of a positive test with the condition (a/[a+c]). Sensitivity ≥0.80 is considered acceptable.bSpecificity is the probability of a negative test without the condition (d/[b+d]). Specificity ≥0.80 is considered acceptable.cPositive predictive value is the probability of the presence of the condition with a positive test result (a/[a+b]).dnegative predictive value is the probability of the absence of the condition with a negative test result (d/[c+d]).

table V. Detection of fenestrations and dehiscences by cBct vs direct methods

Fenestrations Dehiscences

Direct Direct

Fen + Fen − Deh + Deh −cBct cBct

Fen + 26 78 Deh + 22 21Fen − 6 336 Deh − 30 373

Fen, Fenestration; Deh, dehiscence; +, present; −, absent.

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detector and charge-coupled device) was about 0.6 mm for the 25-cm FOV.

the loss in low contrast resolution as stated by Haaga et al50 might explain the inability to distinguish the interface or margin between 2 objects of similar den-sities such as the cementum on root surface and alveolar bone. the densities of cementum and bone are similar because of their similar hydroxyapatite content.18 ce-mentum has 45% to 50% hydroxyapatite, and bone has about 65%. enamel, on the other hand, has a hydroxy-apatite content of about 97%, thus resulting in a greater density difference between cementum and enamel than between cementum and bone. therefore, this density difference might explain why the ceJs were more ac-curately and reliably measured than the cementum-bone interfaces (correlation coefficient of 0.94 vs 0.87). ad-ditionally, BM had a certain thickness that might have caused difficulty in selecting the point accurately for the measurement.

Using mandibles predrilled with reference holes, Kobayashi et al9 reported a mean measurement error (mean absolute difference) of 0.22 mm (± 0.15) to the BM between cBct and direct measurements; this was less than that found in this study of 0.6 mm (± 0.8). as discussed previously, this difference is explained by the smaller voxel used in their study (0.125 mm) and the more well-defined reference points in the artificially created defects. Using a mean absolute measurement er-ror, Mischkowski et al5 reported a similar accuracy of 0.26 mm (± 0.18 mm) on measurements also made on fabricated holes at predefined distances on a dry skull. their voxel size was 0.30 mm, but the accuracy might have been overestimated compared with clinical settings because of the use of gutta percha points placed at the holes to improve visualization during measurements.

Of the previous studies performed to evaluate the ac-curacy of cBct measurements, only several reported on the reliability of the method by repeating measurements

of fenestration) was truly positive, was only 0.25. the negative predictive value for dehiscences was 0.93, and the positive predictive value was only 0.51. Sixteen false-positive dehiscences were excluded by examining axial and coronal slices, and 2 true-positive dehiscences were eliminated. For fenestrations, 57 false positives were excluded when slice data were examined, and no true positives were eliminated (table Vi).

the icc values for the 4 continuous variables, t-ceJ, t-BM, t-Fen1, and t-Fen2, showed excellent re-liability for the direct (digital caliper) method with coef-ficients at 0.99, and the reliability for the cBct method was very good to excellent with coefficients from 0.89 to 0.95 (tables Viii and iX).

dISCuSSIon

One aim of this study was to evaluate the accuracy and reliability of linear measurements of alveolar bone height with cBct. to measure alveolar bone height re-quires identification of the alveolar BM and the ceJ. the accuracy of detection of these landmarks was mea-sured independently. interestingly, the identification of the ceJ was more accurate than that of the BM. this finding is understandable because of the cBct images. the ceJ is the junction between enamel and cemen-tum, 2 biologic tissues with different densities. the ac-curacy of identifying this intersection is limited by the size of each voxel in the image. therefore, the ceJ on the cBct images used in this study should theoretically be able to be located within the margin of error of a single voxel, or about 0.38 mm. the actual margin of error was 0.4 mm. in contrast to the ceJ, the alveolar BM is the junction between cementum and bone, 2 tis-sues with similar densities. Here, the accuracy is limited not by voxel size but by the physical spatial resolution of the image. the physical spatial resolution of a ct image is determined by testing with a resolution phan-tom. For 2 ma, 12-in cBct images on the Hitachi cB Mercuray, the physical resolution is 0.668 mm. the results of this study are consistent with this physical resolution limit, since the BM was located with an accu-racy of 0.6 mm. Both spiral ct and multislice ct have higher physical resolutions, so they might yield slightly better results, but there is a 10-fold increase in radiation with these methods. likewise, cBct machines with lower milliampere settings might have higher margins for error in locating the BM. Ballrick et al48 demon-strated that the average image resolution for the clear separation of 4 lines on cBct (with a flat-panel detec-tor) was 0.622 mm for the 6-cmFOV and 0.860 mm for 13-cmFOV, whereas Baba et al49 demonstrated that the resolution of the cBct (with an image-intensifier

table VII. analysis of artifacts by cortical bone thickness

Cross sectionsSites with bone (n)

Mean ± SD (mm)

Minimum (mm)*

Maximum (mm)†

Dehiscence artifactsaxial 18 0.8 ± 0.2 0.6 1.2coronal 17 0.9 ± 0.2 0.6 1.3

Fenestration artifactsaxial 57 1.0 ± 0.3 0.6 1.7coronal 56 1.0 ± 0.2 0.7 1.7

*Minimum thickness of buccal cortical bone overlying root.†Maximum thickness of buccal cortical bone overlying root.

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higher rate of false positives (false fenestrations) with cBct: 3 times the number of fenestrations detected on cBct compared with direct skull examination. along with false positives, there were also a sig-nificant number of false negatives, with true defects missed on cBct. More than half of the dehiscences were not detected on cBct (30 of 52 dehiscences; data not shown).

comparing our results with those of Fuhrmann,31 in which a conventional ct (high resolution) was used to assess dehiscences and fenestrations artificially created on human skulls, we demonstrated higher sensitivity of cBct for fenestrations (80% vs 70% for ct), but low-er sensitivity for dehiscences (42% vs to 70% for ct). More true dehiscences were missed on cBct compared with ct. this is probably because the BM tapered to a thickness less than the physical limits of the cBct, and therefore the BM could only be identified within this 0.6-mm limit.

the spatial resolution limitations of the cBct meant that areas with bone less than 0.6 mm thick were seen on the image as areas without bone. the extent of bone thickness required to be depicted on cBct was elucidated by the bone thicknesses of the false-positive defects measured on axial and coronal slice data (table Vii). the smallest thickness measured on axial and coronal sections was 0.6 mm, suggesting that this was the minimum thickness required for bone to be measurable and distinguishable from the root surface. this required minimum bone thickness might partially explain the higher number of false-positive fenestrations in the maxilla, where the cortical bone is less dense than that of the mandible.51 another reason for the increased number of false-positive fenestrations in the maxilla could be the higher prevalence of root prominence in

on a small sample with a time interval between the first and second measures. Pinsky et al6 found that the in-traexaminer reliabililty by icc for cBct ranged from 0.75 to 0.99. Baumgaertel et al47 found that the reliabil-ity of measuring variables relating to teeth on cBct images was highly reliable with an icc nearly 1.0. this study also showed high reliability of both cBct and di-rect methods with an intraclass correlations of 0.94 and 0.99, respectively. the slight decrease in reliability for cBct can be attributed to the difficulty in visualizing the ceJ or the BM as clearly as the crowns of the teeth.

a second aim was to evaluate the accuracy and re-liability of cBct for diagnosing natural buccal alveo-lar fenestrations and dehiscences on dry human skulls. naturally occurring fenestrations and dehiscences were used because previous studies used artificially created defects on phantoms or dry skulls, where the detection of defects can be overestimated because of the distinct bor-ders created by the operator. Mengel et al3 reported that all dehiscences and fenestrations in pig and dry human mandibles were identifiable on the cBct; however, these were artificially created, and gutta percha points were used to aid visualization. Misch et al4 also reported that all periodontal defects, artificially created on a mandible, were identifiable and measurable. Similarly, Pinsky et al6 identified bony defects and cavitations on human mandi-bles and acrylic blocks, but, again, these were artificially created. Since natural defects have more gradual and ta-pering margins, they might not be visualized on cBct as easily as those created by an operator. therefore, these studies might not provide a true assessment of cBct for diagnosing alveolar bone defects.

Our results showed that the indirect assessment of buccal alveolar bone defects overlying roots was not as accurate as previously reported. there was a much

table VIII. intraoperator reliability for t-ceJ and t-BM measurements at times 1 (t1) and 2 (t2) by means, mean differences, standard deviations, and icc

Direct CBCT

n = 91T1

Mean ± SD (mm)T2

Mean ± SD (mm) ICCT1

Mean ± SD (mm)T2

Mean ± SD (mm) ICC

t-ceJ 8.2 ± 1.6 8.3 ± 1.5 0.987 7.9 ± 1.6 8.0 ± 1.6 0.948t-BM 10.1 ± 2.2 10.2 ± 2.1 0.991 10.0 ± 2.0 10.1 ± 2.0 0.935

table IX. intraoperator reliability for t-Fen1 and t-Fen2 measurements at times 1 (t1) and 2 (t2) by means, mean differences, standard deviations, and icc

Direct CBCT

n = 11T1

Mean ± SD (mm)T2

Mean ± SD (mm) ICCT1

Mean ± SD (mm)T2

Mean ± SD (mm) ICC

t-Fen1 14.9 ± 2.0 14.8 ± 2.1 0.992 14.1 ± 3.2 14.0 ± 2.8 0.937t-Fen2 17.9 ± 1.9 18.0 ± 1.8 0.994 17.8 ± 2.7 17.8 ± 2.9 0.891

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provide evidence that, when a defect is not found on cBct, most likely it is not there; this gives some assur-ance that a buccal defect is probably not present.

as with most studies, this study had some limita-tions. First, the cBct scanner we used was calibrated routinely with a designated phantom with densities simulating a live person, but our dry skulls did not have any soft tissue. Soft tissues have attenuation co-efficients that can affect the x-ray beam going through the skull and hence the final image. the final image depends on the algorithms of the calibration process. Since the standard for calibration was for a live person, the calibration might not have been optimal for the dry skulls. calibration is an important step in primary reconstruction of scanned images to eliminate recon-struction inaccuracies and errors from the imaging sys-tem. Without proper calibration, the images can have excessive artifacts. thus, perhaps, the machine could have been calibrated with a more appropriate standard to sufficiently eliminate any inherent imaging artifacts. additionally, because the skulls were from a museum collection, it was not possible to provide some resem-blance of soft tissue, such as balloons filled with water as done by Hilgers et al.53 alternatively, cadaver heads with soft tissues could be used to better simulate a live person. However, the problem from this approach might be a limited sample size with a sufficient num-ber of defects for the study.

another potential limitation of this study was the possible operator error introduced by fixing the Houn-sfield threshold window for all skulls. the Hounsfield values for the upper and lower limits of the window were based on a histogram study of 1 skull. However, because of the effects of thickness and radiodensity of the subject on the attenuation of radiation and the resulting image, that threshold might not have been optimal for all skulls.57 each skull could have been optimized individually. One way to amend this prob-lem could be to use an operator-independent and a less subjective method of classifying defects, such as the region-of-interest tool and identifying bony defects based on segmentation methods. the defect could be identified more objectively by using the Hounsfield histogram for the segmented area. the difference be-tween the bone surface and root might be more appar-ent by examining the Hounsfield values.

ConCLuSIonS

this study showed that measurements on cBct were not as accurate as direct measurements on skulls. the differences between the direct and cBct methods were most likely due to limitations in spatial resolution

the maxilla. root prominence influences the overlying alveolar bone thickness. the overlying bone tends to be thinner where the root is prominent.38,40,42 nevertheless, our study showed 2 possibilities when bone was not vi-sualized on cBct: the bone might be truly missing, or its thickness was less than 0.6 mm.

the ability to visualize 2 objects close together might also depend on image quality, which is influenced by the scanning parameters. the effect of milli amperage on image quality has been studied extensively. com-paring ct images taken at various settings from 6 to 100 ma, Haaga et al50 found a loss in low contrast reso-lution when the lower milliamperage settings were used (6 and 20 ma), whereas the resolution was the same at 40 and 100 ma. Palomo et al52 also found a difference in image resolution that depended on the milliamper-age. Using a c-phantom with an acrylic base, a series of metal lines in water, and the method of Q-sort con-ducted by professionals experienced with radiographs, they showed that higher milliamperage with a copper filter gave better image quality and higher spatial reso-lution. However, they suggested that for dental use a compromise between image quality and radiation dose should be considered based on the “as low as reasonably achievable” principle.

thus, the effect of different milliamperage set-tings might be a factor in the differences we observed compared with previous studies. Misch et al4 and Pin-sky et al6 used scanning parameters that were much higher than our clinical parameters. Misch el al4 used 47.7 ma, 120 kVp, and 20 seconds, and Pinsky et al6 used 98 ma, 120 kVp, and 20 seconds. Both studies demonstrated that all artificially created alveolar bone defects were identified, and measurement accuracy was high. Similarly, Mischkowski et al5 used 28 ma com-pared with studies reporting lower measurement accu-racy, such as that of Hilgers et al,53 who used 1 to 3 ma, and that of lascala et al,54 who used 7 ma. Studies that showed lower accuracy or sensitivity as in our study also used lower tube currents. Honda et al55 used 2 ma, 80 kVp, and 17 seconds, whereas Hintze et al56 used an even lower milliamperage of 0.5 ma, 110 kVp, and 5 to 7 seconds.

the results still support the use of cBct for de-tection of buccal bony defects such as dehiscences and fenestrations. the low positive predictive values for de-hiscences and fenestrations are less critical, since the prevalences of these defects are low at about or less than 10% as reported in most studies.38,40,42,43 Because of the low prevalence, it becomes more important to identify true negatives correctly to avoid unnecessary alarm. thus, the high negative predictive values of 0.95 for dehiscences and 0.98 for fenestrations in this study

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implant planning using conventional radiography and comput-ed tomography. Dentomaxillofac radiol 2001;30:255-9.

12. Mah JK, Danforth ra, Bumann a, Hatcher D. radiation ab-sorbed in maxillofacial imaging with a new dental computed tomography device. Oral Surg Oral Med Oral Pathol Oral ra-diol endod 2003;96:508-13.

13. Scaf g, lurie ag, Mosier KM, Kantor Ml, ramsby gr, Freedman Ml. Dosimetry and cost of imaging osseointegrated implants with film-based and computed tomography. Oral Surg Oral Med Oral Pathol Oral radiol endod 1997;83:41-8.

14. Hoffman ea, Sinak lJ, robb ra, ritman el. noninvasive quantitative imaging of shape and volume of lungs. J appl Physiol 1983;54:1414-21.

15. ritman el, Kinsey JH, robb ra, gilbert BK, Harris lD, Wood eH. three-dimensional imaging of heart, lungs, and cir-culation. Science 1980;210:273-80.

16. iwasaki t, ritman el, Fiksen-Olsen MJ, romero Jc, Knox Fg. renal cortical perfusion--preliminary experience with the dynamic spatial reconstructor (DSr). ann Biomed eng 1985;13:259-71.

17. Scarfe Wc, Farman ag, Sukovic P. clinical applications of cone-beam computed tomography in dental practice. J can Dent assoc 2006;72:75-80.

18. carranza F, newman M, takei H. the tooth-supporting struc-tures. clinical periodontology. 9th ed. Philadephia: W. B. Saun-ders; 2002.

19. ericsson i, thilander B, lindhe J, Okamoto H. the effect of orthodontic tilting movements on the periodontal tissues of in-fected and non-infected dentitions in dogs. J clin Periodontol 1977;4:278-93.

20. Wennstrom Jl, Stokland Bl, nyman S, thilander B. Peri-odontal tissue response to orthodontic movement of teeth with infrabony pockets. am J Orthod Dentofacial Orthop 1993;103:313-9.

21. Årtun J, Urbye KS. the effect of orthodontic treatment on peri-odontal bone support in patients with advanced loss of marginal periodontium. am J Orthod Dentofacial Orthop 1988;93:143-8.

22. Zachrisson BU, alnaes l. Periodontal condition in orthodonti-cally treated and untreated individuals. i. loss of attachment, gingival pocket depth and clinical crown height. angle Orthod 1974;43:402-11.

23. Wehrbein H, Bauer W, Diedrich P. Mandibular incisors, alveolar bone, and symphysis after orthodontic treatment. a retrospec-tive study. am J Orthod Dentofacial Orthop 1996;110:239-46.

24. Karring t, nyman S, thilander B, Magnusson i. Bone regen-eration in orthodontically produced alveolar bone dehiscences. J Periodontal res 1982;17:309-15.

25. Wainwright WM. Faciolingual tooth movement: its influence on the root and cortical plate. am J Orthod 1973;64:278-302.

26. garib Dg, Henriques JF, Janson g, de Freitas Mr, Fernandes aY. Periodontal effects of rapid maxillary expansion with tooth-tissue-borne and tooth-borne expanders: a computed tomography evaluation. am J Orthod Dentofacial Orthop 2006;129:749-58.

27. Zachrisson BU, alnaes l. Periodontal condition in orthodonti-cally treated and untreated individuals. ii. alveolar bone loss: radiographic findings. angle Orthod 1974;44:48-55.

28. Sarikaya S, Haydar B, ciger S, ariyurek M. changes in al-veolar bone thickness due to retraction of anterior teeth. am J Orthod Dentofacial Orthop 2002;122:15-26.

29. lang nP, Hill rW. radiographs in periodontics. J clin Peri-odontol 1977;4:16-28.

of the cBct images. location of the ceJ was accu-rate to within 0.4 mm, and location of the BM to with-in 0.6 mm. the correlation between cBct and direct measurements was high for measurements to the ceJ (r = 0.94) and the BM (r = 0.87). the reliability of the cBct method was high, with an icc of about 0.95.

the diagnostic value of cBct for the detection of buccal defects was high for fenestrations: both sensi-tivity and specificity were about 0.80. For dehiscences, the specificity was high at 0.95, but the sensitivity was low at 0.40. the positive predictive values were 0.50 for dehiscences and 0.25 for fenestrations. in other words, when a defect was found on cBct, it was a true dehiscence about half of the time and a true fenestra-tion about a quarter of the time. the negative predictive values, however, were high for both at 0.93 for dehis-cences and 0.98 for fenestrations. this meant that, when a defect was not found on cBct, most likely there was no defect.

ReFeRenCeS

1. loubele M, Maes F, Schutyser F, Marchal g, Jacobs r, Suetens P. assessment of bone segmentation quality of cone-beam ct versus multislice spiral ct: a pilot study. Oral Surg Oral Med Oral Pathol Oral radiol endod 2006;102:225-34.

2. Marmulla r, Wortche r, Muhling J, Hassfeld S. geometric ac-curacy of the newtom 9000 cone beam ct. Dentomaxillofac radiol 2005;34:28-31.

3. Mengel r, candir M, Shiratori K, Flores-de-Jacoby l. Digital volume tomography in the diagnosis of periodontal defects: an in vitro study on native pig and human mandibles. J Periodontol 2005;76:665-73.

4. Misch Ka, Yi eS, Sarment DP. accuracy of cone beam com-puted tomography for periodontal defect measurements. J Peri-odontol 2006;77:1261-6.

5. Mischkowski ra, Pulsfort r, ritter l, neugebauer J, Brochha-gen Hg, Keeve e, et al. geometric accuracy of a newly devel-oped cone-beam device for maxillofacial imaging. Oral Surg Oral Med Oral Pathol Oral radiol endod 2007;104:551-9.

6. Pinsky HM, Dyda S, Pinsky rW, Misch Ka, Sarment DP. ac-curacy of three-dimensional measurements using cone-beam ct. Dentomaxillofac radiol 2006;35:410-6.

7. Hashimoto K, Kawashima S, araki M, iwai K, Sawada K, akiyama Y. comparison of image performance between cone-beam computed tomography for dental use and four-row multi-detector helical ct. J Oral Sci 2006;48:27-34.

8. Hu H, He HD, Foley WD, Fox SH. Four multidetector-row heli-cal ct: image quality and volume coverage speed. radiology 2000;215:55-62.

9. Kobayashi K, Shimoda S, nakagawa Y, Yamamoto a. ac-curacy in measurement of distance using limited cone-beam computerized tomography. int J Oral Maxillofac implants 2004;19:228-31.

10. Karger cP, Hipp P, Henze M, echner g, Hoss a, Schad l, et al. Stereotactic imaging for radiotherapy: accuracy of ct, Mri, Pet and SPect. Phys Med Biol 2003;48:211-21.

11. lecomber ar, Yoneyama Y, lovelock DJ, Hosoi t, adams aM. comparison of patient dose from imaging protocols for dental

S109-119_AAOPRG_3049.indd 118 3/24/10 12:15 PM


configuration and physical properties. Dentomaxillofac radiol 2004;33:51-9.

46. Stahl S, cantor M, Zwig e. Fenestrations of the labial alveolar plate in human skulls. J am Soc Periodontists 1963;1:99-102.

47. Baumgaertel S, Palomo JM, Palomo l, Hans Mg. reliability and accuracy of cone-beam computed tomography dental mea-surements. am J Orthod Dentofacial Orthop 2009;136:19-28.

48. Ballrick J, Palomo JM, ruch e, amberman BD, Hans Mg. im-age distortion and spatial resolution of a commercially avail-able cone-beam computed tomography machine. am J Orthod Dentofacial Orthop 2008;134:573-82.

49. Baba r, Ueda K, Kuba a, Kohda e, Shiraga n, Sanmiya t. Development of a subject-standing-type cone-beam computed tomography for chest and orthopedic imaging. Front Med Biol eng 2001;11:177-89.

50. Haaga Jr, Miraldi F, Macintyre W, liPuma JP, Bryan PJ, Wi-esen e. the effect of mas variation upon computed tomogra-phy image quality as evaluated by in vivo and in vitro studies. radiology 1981;138:449-54.

51. Park HS, lee YJ, Jeong SH, Kwon tg. Density of the alveolar and basal bones of the maxilla and the mandible. am J Orthod Dentofacial Orthop 2008;133:30-7.

52. Palomo J, Subramanyan K, Hans M. influence of ma settings and a copper filter in cBct image resolution. int J comput as-sist radiol Surg 2006;1:391-3.

53. Hilgers Ml, Scarfe Wc, Scheetz JP, Farman ag. accuracy of linear temporomandibular joint measurements with cone-beam computed tomography and digital cephalometric radiography. am J Orthod Dentofacial Orthop 2005;128:803-11.

54. lascala ca, Panella J, Marques MM. analysis of the ac-curacy of linear measurements obtained by cone beam com-puted tomography (cBct-newtom). Dentomaxillofac radiol 2004;33:291-4.

55. Honda K, larheim ta, Maruhashi K, Matsumoto K, iwai K. Osseous abnormalities of the mandibular condyle: diagnostic reliability of cone beam computed tomography compared with helical computed tomography based on an autopsy material. Dentomaxillofac radiol 2006;35:152-7.

55. White S, Pharoah M. computed tomography. in: White S, edi-tor. Oral radiology: principles and interpretation. 4th ed. St louis: Mosby; 2000.

56. Hintze H, Wiese M, Wenzel a. cone beam ct and convention-al tomography for the detection of morphological temporoman-dibular joint changes. Dentomaxillofac radiol 2007;36:192-7.

30. rees tD, Biggs nl, collings cK. radiographic interpretation of periodontal osseous lesions. Oral Surg Oral Med Oral Pathol 1971;32:141-53.

31. Fuhrmann r. three-dimensional interpretation of alveolar bone dehiscences. an anatomical-radiological study—part i. J Orofac Orthop 1996;57:62-74.

32. rothe le, Bollen aM, little rM, Herring SW, chaison JB, chen cS, et al. trabecular and cortical bone as risk factors for orthodontic relapse. am J Orthod Dentofacial Orthop 2006;130:476-84.

33. ericsson i, thilander B. Orthodontic relapse in dentitions with reduced periodontal support: an experimental study in dogs. eur J Orthod 1980;2:51-7.

34. Melsen B, allais D. Factors of importance for the development of dehiscences during labial movement of mandibular incisors: a retrospective study of adult orthodontic patients. am J Orthod Dentofacial Orthop 2005;127:552-61.

35. Wennstrom Jl. Mucogingival considerations in orthodontic treatment. Semin Orthod 1996;2:46-54.

36. Wennstrom Jl, lindhe J, Sinclair F, thilander B. Some peri-odontal tissue reactions to orthodontic tooth movement in mon-keys. J clin Periodontol 1987;14:121-9.

37. Yared KFg, Zenobio eg, Pacheco W. Periodontal status of mandibular central incisors after orthodontic proclination in adults. am J Orthod Dentofacial Orthop 2006;130:6.e1-8.

38. abdelmalek rg, Bissada nF. incidence and distribution of al-veolar bony dehiscence and fenestration in dry human egyptian jaws. J Periodontol 1973;44:586-8.

39. Davies rM, Downer Mc, Hull PS, lennon Ma. alveolar de-fects in human skulls. J clin Periodontol 1974;1:107-11.

40. edel a. alveolar bone fenestrations and dehiscences in dry Bedouin jaws. J clin Periodontol 1981;8:491-9.

41. Jorgic-Srdjak K, Plancak D, Bosnjak a, azinovic Z. incidence and distribution of dehiscences and fenestrations on human skulls. coll antropol 1998;22 (Suppl):111-6.

42. larato Dc. alveolar plate fenestrations and dehiscences of the human skull. Oral Surg Oral Med Oral Pathol 1970;29:816-9.

43. rupprecht rD, Horning gM, nicoll BK, cohen Me. Preva-lence of dehiscences and fenestrations in modern american skulls. J Periodontol 2001;72:722-9.

44. Hulley S, cummings S. Designing clinical research. 2nd ed. Philadelphia: lippincott-raven Publishers; 2001.

45. araki K, Maki K, Seki K, Sakamaki K, Harata Y, Sakaino r, et al. characteristics of a newly developed dentomaxillo-facial x-ray cone beam ct scanner (cB Mercuray): system

S109-119_AAOPRG_3049.indd 119 3/24/10 12:15 PM

Documents

Accuracy and reliability of cone-beam computed tomography for measuring alveolar bone height and detecting bony dehiscences and fenestrations